from my svn 855

when it is unrequired.

2. Two new NeonOptimized functions subtract_8u8u32f and subtract_8u8u8s were added

2. Two new NeonOptimized functions subtract_8u8u32f and subtract_8u8u8s were added

Conflicts:
	modules/core/src/arithm.cpp

ORB_GPU::downloadKeyPoints
ORB_GPU::convertKeyPoints

2. Two new NeonOptimized functions subtract_8u8u32f and subtract_8u8u8s were added

* reorder arguments
* rewrite accuracy tests
* replace doubles with integer arithmetic inside the main loop